Driving Niagara Parameters via Scene Graph Variables

What you'll learn

• How Verse reads and updates Scene Graph variables tied to Niagara emitters.
• Synchronizing visual feedback with gameplay state using player UI APIs.
• Writing performant, suspending loops that drive continuous parameter updates.

How it works

When you place a Niagara System in Scene Graph, you can expose custom variables and bind them directly to emitter parameters (scale, color, spawn rate, etc.). Instead of relying on static editor values, Verse can compute these values on the fly and push them down to the visuals. To ensure players are aware of these dynamic changes, we wire up a feedback loop that broadcasts the current parameter state to every connected player's canvas.

Let's build it

This device simulates the core driver pattern: a continuous coroutine that increments a parameter (representing the Scene Graph variable feeding your Niagara chain) and pushes the live value to player UIs using GetPlayerUI[] and AddWidget.

using { /Verse.org }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/Diagnostics }
using { /Fortnite.com/Devices }

niagara_scene_driver := class<concrete>(creative_device):

    @editable
    // Represents the Scene Graph variable driving your Niagara emitter
    TargetParam : float = 0.0

    Running : logic = true

    OnBegin<override>()<suspends>: void =
        loop:
            if (Running?):
                // In a real map, this is where you'd assign to the Scene Graph variable
                set TargetParam += 1.5
                Print("Driving Niagara parameter to {TargetParam}")

                // Push real-time feedback to every player's screen
                if (Players := GetPlayspace().GetPlayers()):
                    for (Player : Players):
                        if (UI := GetPlayerUI[Player]):
                            UI.AddWidget(text_block_widget{
                                Text: "Scene Graph Param: {TargetParam}"
                            })
                
                // Yield to prevent CPU hugging while updating visuals
                Sleep(0.2)
            else:
                Sleep(0.1)

Try it yourself

1. Place a Niagara System Emitter in Scene Graph.
2. Open its parameters and create a new Float variable.
3. Map that variable to an emitter's Scale or Color parameter.
4. Place this device in your level, play, and watch the particles react to the UI feedback loop.

Recap

• Scene Graph variables allow Verse to control Niagara in real-time.
• GetPlayerUI[] and AddWidget let you push dynamic status updates directly to players.
• Sleep keeps your parameter loop performant by yielding between updates.